A traveler submitted this question about the express lanes for Monday’s online chat, and I thought I’d respond to it here.

I haven’t heard much about how the new HOT lanes will work. I drive from Springfield to District everyday and use HOV. I pick up slugs in the morning and often leave after 6 p.m. It often takes me longer to get from the Pentagon over the 14th Street Bridge than it does to get from Springfield to the Pentagon and I am skeptical and concerned as to how it is going to work with the new HOT lanes dumping into the HOV lanes once you leave Fairfax County.

I also have been wondering, once the HOT lanes are up, will I have to pay to use the lanes after 6 p.m.? I don’t feel like there has been a lot of information out there about how these will work.

What’s the same: Once the HOT lanes are operating, a driver still could pick up slugs in the morning and travel north in the middle lanes to the District. The HOT lanes will end just north of the Beltway, and after that, it’s the same old HOV lanes to the 14th Street Bridge. For toll-paying drivers, the system will be the same as on the Beltway express lanes. There’s no upper limit on the tolls, which are collected electronically. The toll will rise and fall depending on the flow of traffic in the express lanes.

The express lanes still are a work in progress. A crew spreads mulch along a new section of the roadway. (Mike Salmon/VDOT)

What’s different: The carpooling driver will need to get an E-ZPass Flex to get the free ride and remember to set the Flex to the carpool mode. As of July, Virginia has stopped charging a monthly maintenance fee on E-ZPass accounts. So the main annoyance of using the E-ZPass Flex may turn out to be remembering to flip the switch for your southbound journey in the afternoon if you didn’t pick up slugs for the homeward trip.

If you don’t have at least two passengers, you will have to pay a toll to use these lanes. The I-95 HOT lanes will operate “24 hours a day, seven days a week,” Kevin Ginnerty said last week. He is the director of project delivery for Transurban, one of the private partners on the 95 Express Lanes project and the operator of the 495 Express Lanes.

And hybrids will stop getting the free ride. The old exemption for clean fuel plates will not apply to drivers in the express lanes.

The driver who submitted the question is concerned about what will happen with the northbound traffic at the point where the HOT lanes go back to being HOV lanes. The driver is right to be concerned. This is the point where the toll payers will need to exit. If they continue north on the I-395 HOV lanes, they will be in violation of the carpooling rules and could be ticketed.

A new flyover ramp should ease that transition to the regular northbound lanes of I-395. So should a new auxiliary lane now under construction on the right side of the northbound lanes.

But it’s tough to know exactly what’s going to happen till it happens. Drivers should get enough warning via new signs, but it’s not that hard to zone out on a long commute.

That’s not the only decision point drivers will face on I-95. These express lanes will be different from the Beltway lanes in that they will offer drivers the option of either getting into them from the regular lanes or out of them and onto the regular lanes along the 29-mile route.

This is different from the Beltway express lanes, where the only opportunities to transition between express lanes and regular lanes is at the start and the end of the system.

The express lanes operators are continuing to develop their marketing and education campaign on all this. It’s a good thing they’re getting that underway well in advance of the opening, because there will be a lot to learn.

Robert Thomson is The Washington Post’s “Dr. Gridlock.” He answers travelers’ questions, listens to their complaints and shares their pain on the roads, trains and buses in the Washington region.

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Comments our editors find particularly useful or relevant are displayed in Top Comments, as are comments by users with these badges: . Replies to those posts appear here, as well as posts by staff writers.